x-axis second line date formatting edge case

[archmoj]

Only on the x-axis when side is bottom?

Good point - same thing happens when ticklabelposition is the default outside and side is 'top'. I'd consider it a bug in both cases.

Originally posted by @alexcjohnson in #5321 (comment)

[archmoj]

Should we follow similar pattern on y-axes with tickangle = +/-90?

[nicolaskruchten]

Should we follow similar pattern on y-axes with tickangle = +/-90?

Ideally yes, but let's not do extra work right now to support that.